Saw and impact resistant lock shackle

ABSTRACT

A lock shackle formed of an elongated metal core having longitudinally extending shallow grooves formed in its surface, and a thin wall tube closely fitted around the core, with the grooves filled with a matrix formed of hard carbide particles and a soft material binder.

United States Patent 1 Shwayder et a1.

[ Dec. 11, 1973 SAW AND IMPACT RESISTANT LOCK SHACKLE [75] Inventors:Warren M. Shwayder; Baruch Sear,

both of Birmingham, Michv [73] Assignee: Warren M. Shwayder, Bloomfield3,447,230 6/1969 Bargainnier 29/420.5

Reich 29/420.5 Miller 70/38 A l/197l l/1973 Primary Examiner-Robert L.Wolfe Attorney-Bernard J. Cantor [57] ABSTRACT A lock shackle formed ofan elongated metal core having longitudinally extending shallow groovesformed in its surface, and a thin wall tube closely fitted around thecore, with the grooves filled with a matrix formed of hard carbideparticles and a soft material binder.

4 Claims, 8 Drawing Figures I SAW AND IMPACT RESISTANT LOCK SHACKLEBACKGROUND OF INVENTION Padlock shackles are generally made of steelrods bent into the U-shape of a shackle and heat treated for hardness.These conventionally used shackles have only a limited resistance to sawcutting and virtually no resistance to cutting by carbide coated sawssuch as rod saws. In addition, they are relatively easily broken by theimpact of a heavy hammer. Moreover, they can be relatively easilystretched or elongated by insertion of chisels or wedges between ashackle loop and padlock casing, so that they can be pulled out of thelocked position. Thus, conventional padlocks, and particularly theirshackles, provide no protection against a determined and sustainedeffort to break them. Thus, the invention herein relates to an improvedshackle which is highly resistant to saw cutting, impact application andstretching.

SUMMARY OF INVENTION The improved shackle herein comprises aconventional appearing, U-shaped, rod-like member, but formed of anelongated, inner core which is generally spline shaped in cross-sectionto provide longitudinally extending, shallow grooves in its surface,with a tubular sleeve closely fitted around the outside of the core, and

. with the grooves filled with a matrix of hard particles,

such as tungsten carbide or the like, in a soft metal .binder. The coreand sleeve are made of a work hardenable steel. The assembly of core,matrix and sleeve is swaged to work harden the metal, elongate and formthe finished diameter of the part, as well as to seal the elementstogether.

The finished rod-like shackle cannot be sawed through or broken byimpact using any conventional means, including the extremely hard typecarbide DESCRIPTION OF DRAWINGS FIG. 1 is a schematic view of a padlockshowing the improved shackle herein.

FIG. 2 is an enlarged cross-sectional view of the shackle taken in thedirection of arrows 2-2 of FIG. 1.

FIG. 3 is an elevational view of the core, per se.

FIG. 4 shows the initial assembly of the sleeve upon the core, and

FIG. 5 shows the step of applying the binder material into the grooveswhich have already been filled with hard particles.

FIG. 6 is a partially cross-sectioned view of the assembled rod-likemember.

FIG. 7 is an elevational view, partially in crosssection, of thefinished shackle.

FIG. 8 is a fragmentary, enlarged cross-sectional view of a portion ofthe shackle.

DETAILED DESCRIPTION FIG. 1 illustrates a conventional padlock 10 havinga shackle 11 which fits into and locks within the padlock casing or body12. The construction and locking parts of the casing are omitted sincethese form no part of the invention herein. A locking bar 13, which isarranged within and forms part of the locking mechanism, isschematically illustrated. This bar engages notches I4 and 15 formed inthe shackle to lock the shackle into the padlock casing. It should beunder stood that the shackle of this invention may be used with any formof padlock casing, regardless of the type of locking mechanism includedtherein.

The shackle is formed of a central core 16 which preferably is roughlyspline-shaped in cross-section and of uniform diameter. The core lowerend 17 may be flared or tapered. The core is thus provided with a numberof longitudinally extending shallow grooves 18 defined by the tooth-likeformation of the spline.

A tubular sheath 19 is closely fitted over the core (see FIG. 4),including force fitting the lower end 20 of the sheath around the flaredend 17 of the core. Additionally, where desired, the lower end 20 may bewelded at 20a to the core lower end. As illustrated in the drawing, thetube is preferably of greater length than the core so that its upper end21 extends a distance above the upper end of the core.

The grooves 18 are filled with a matrix 22 formed of hard particles 23(see FIG. 8) and a binder 24. The particles are preferably of a hardmetal carbide such as tungsten carbide, either cast or cemented, orother similar carbide particles which have high degrees of hardness. Thebinder may be of a soft metal material, such as copper braze or othersuitable brazing materials. The particles are closely packed within thegrooves and the spaces between them are filled with the binder to form asolid matrix.

METHOD OF MAKING SHACKLE A method of forming the improved shackle hereinis as follows: First, the core 16 is formed with the longitudinallyextending shallow grooves and the flared end 17 (see FIG. 3). Next, thethin walled tubular sheath is forced into position around the core, asillustrated in FIG. 4. Then, the hard'particles are poured into thegrooves, with the rod arranged upright as shown in FIG. 5, to form apacking of particles within the grooves. The space at the upper end 21of the tube 19 may then be filled with pellets or beads or powder of thebrazing compound, such as copper brazing pellets 25, and while the rodis held upright, it is heated to melt the braze which flows downwardly,filling the spaces be tween the particles. Preferably enough braze isplaced into the tube, so that the upper end 21 of the tube is filledwith braze material above the upper end of the core. When the rod ispermitted to cool and the braze to solidify, a slug 26 of braze fillsthe upper end of the sheath (see FIG. 6).

Next, the composite rod is swaged to reduce its diameter to requiredsize, while simultaneously elongating it and more importantly, workhardening the metal forming the sleeve and the core. Both of thesemetals are selected from the work hardenable steels, with the tubepreferably being of a stainless steel material to provide a greatertoughness, corrosion resistance, improved appearance, etc.

After the swaging, the rod is of uniform cross-section, the flaredportion being reduced to the common diameter of the rod.

Thereafter, the rod may be bent into the U-shaped shackle formillustrated in FIG. 7 and the notches l4 and formed therein. The notch14 may be easily cut into the shackle since it is arranged in the areaof the end of the core where there is no matrix material. On the otherhand, the notch 15, located in an area where there is matrix material,may be formed either by a suitable deformation process or electrical orheat cutting method.

Alternatively, the area into which the notch 15 is formed may be madewithout the groove and matrix so as to permit easy notching.

The portion of the shackle below the notch 15, that is, where the slug26 of braze fills the tube, is concealed within the padlock casing anddoes not carry any unexpected loads. Thus, the slug 26 simply functionsas a filler, as a place where openings may be easily drilled through forvarious types of locking mechanisms, and also as a heat conductor toremove heat which may be applied to the shackle.

EXAMPLE OF CONSTRUCTION While the materials and the sizes and shape ofthe shackle may vary, an example of its construction is as follows: Aone-half inch diameter spline formed of work hardenable 304 stainlesssteel rod was provided with six grooves, equally spaced apart around itssurface, the grooves being approximately 0.12 wide by 0.08 deep. Thegrooves were filled with cemented tungsten carbide grit of approximately12/20 mesh size. The tube or sheath was made of approximatelyninesixteenths outside diameter, with a wall thickness of approximately0.028 inches and formed of 304 stainless steel tubing. Conventionalcopper braze was used as the binder.

After the assembly, the rod was swaged down to a little less thanone-half inch in diameter. The swaging also work hardened the materialto roughly Rockwell c-l0.

The bent shackle resisted penetration by and destroyed all availablesaws, including carbide coated ones of the rod-saw type, sustained inexcess of 16,000 pounds tensile test and resisted breakage by repeatedpounding with a conventional four pound hammer. All of the foregoingresults were far in excess of any possible results achieveable inconventional shackles.

While the rod-like construction and method are described in connectionwith shackles for padlocks, it may likewise be used in otherapplications where similar types of penetration resistance, impactresistance and stretching resistance is desired, such as for example,protective bars, jail bars, locking bars, etc. Likewise, thecross-sectional shape may be varied as may the shape of the grooves orpassageways or spaces which are arranged between the core and thesheath.

Having fully described an operative embodiment of this invention, we nowclaim.

1. In a lock shackle formed of an elongated, rod-like member bent into ashackle shape, the improvement comprising:

said member being formed of an elongated metal core surrounded by aclosely fitting, thin metal sheath, with longitudinally extendingshallow passageways formed between the core and the sheath;

said passageways being filled with a matrix formed of closely packedparticles of a hard material, such as a metal carbide, and a bindermaterial.

2. A construction as defined in claim 1, and said core beingapproximately spline shaped in cross-section, that is, withlongitudinally extending tooth-shaped formations arranged around itsperiphery to define said passageways therebetween, and said sheath beingin the form of a metal tube closely fitted upon the core for contactwith the outer peripheral surfaces of said tooth formations.

3. A construction as defined in claim 2, and the sheath having an endportion extending a distance beyond one end of the core and filled withbinder material, with the opposite end of the core having a short endportion which is ungrooved and in full surface to surface contact withthe adjacent interior surface of the sheath.

4. A construction as defined in claim 1, and said metal beingcharacterized by being work hardenable,

and said member being work hardened.

2. A construction as defined in claim 1, and said core beingapproximately spline shaped in cross-section, that is, withlongitudinally extending tooth-shaped formations arranged around itsperiphery to define said passageways therebetween, and said sheath beingin the form of a metal tube closely fitted upon the core for contactwith the outer peripheral surfaces of said tooth formations.
 3. Aconstruction as defined in claim 2, and the sheath having an end portionextending a distance beyond one end of the core and filled with bindermaterial, with the opposite end of the core having a short end portionwhich is ungrooved and in full surface to surface contact with theadjacent interior surface of the sheath.
 4. A construction as defined inclaim 1, and said metal being characterized by being work hardenable,and said member being work hardened.